The invention relates to automatic control systems and to override arrangements for such systems.
More specifically, though not exclusively, the invention relates to speed control systems for motor road vehicles by means of which the driver may set the vehicle to run at a desired speed which is thereafter automatically maintained by the system (within the limits of available power and having regard to road conditions). In such systems, it is known to provide an override by which it is intended that the system be automatically cut out of operation when the driver applies the brakes of the vehicle. It is obviously important that such an override be effective. A known form of override involves an electrical switch in series with an electrical coil, the switch being intended to be opened by the override so as to disconnect the coil from a source of electrical energization, the de-energized coil then cutting the system out of operation. A disadvantage of such an override is that it will not be effective if the switch sticks or otherwise fails to open when the brakes of the vehicle are applied.
Accordingly, an object of the invention is an improved override arrangement for putting out of action an automatic control system.